The present invention relates to an electrochemical cell and, more particularly, to a primary electrochemical cell insensitive to physical position or orientation.
The majority of electrochemical cells, especially large cells employing a liquid electrolyte solution, ordinarily operate in a particular physical position or orientation, for example, in a vertical upright position. These cells generally include an electrochemical system comprising one or more cathode electrodes, separators, and an electrolyte solution in contact with these elements. The cell elements, commonly referred to as the battery stack, are generally positioned at the bottom of the cell and completely covered with the electrolyte solution. A reservoir is normally provided above the battery stack for containing a sufficient amount of the electrolyte solution to insure that the battery stack is completely covered by the electrolyte solution. This reservoir is especially important in a cell employing a liquid electrolyte solution which is chemically consumed, that is, undergoes a volume loss, during normal operation of the cell. In this case, the reservoir contains a sufficient amount of electrolyte solution to insure that the battery stack is continuously supplied with electrolyte solution over the normal expected life span, or discharge cycle, of the cell. An example of an electrochemical cell of the above type is described in detail in U.S. Pat. No. 4,161,063, in the names of Franz Goebel and Nikola Marincic, and assigned to GTE Laboratories Incorporated. Electrochemical cells constructed in accordance with the above patent generally include a plurality of oxidizable active anodes, a plurality of cathode current collector electrode structures arranged in alternation with the anodes, and a cathodelectrolyte solution in contact with the anodes and cathode current collector structures and comprising a reducible soluble cathode and an electrolyte solute dissolved therein. In a preferred construction of a cell, the oxidizable active anodes are formed of an oxidizable active alkaline metal such as lithium, the cathode current collector electrode structures include carbon black material, and the cathodelectrolyte solution comprises thionyl chloride (reducible soluble cathode) and lithium tetrachloroaluminate (electrolyte solute) dissolved in the thionyl chloride.
As mentioned hereinabove, large electrochemical cells of the abovedescribed type have a specified physical operating position or orientation over the discharge cycle, specifically, an upright vertical position. However, in small calls employing a consumable cathodelectrolyte solution, for example, of a type disclosed in U.S. Pat. No. 4,060,668 in the name of Franz Goebel, an upright vertical position during discharge cannot be guaranteed and it is therefore possible and likely for such a cell to be used for long periods of time in an upside down position and/or on the side. Under these circumstances, and especially as the cathodelectrolyte solution is consumed, it is possible for the battery stack to be denied sufficient electrolyte solution over the discharge cycle of the cell. As a result of this electrolyte "starvation", the cell is very likely to undergo capacity losses, a lower voltage profile, and a possible undesirable increase in operating temperature of the cell, leading to possible physical damage to the cell.